Method of producing puffed pulp



Nov., 3, 1931. J. E. PLUMSTEAD 1,830,131

v I METHOD OF PRQDUCING PUFFED PULP Filed May 9. 1929 2 sheets-sheet 1 oja 2p PULP Pl/FF/Ns oPERAr/a/v FLOW SWEET 0F PULP MILL OPERATION ATTORNEYS.

Patented Nov. 3, 1931 UNITED STATESIPATENT OFFICE "I'OSZIELPIB E. PL'UMSTEAD, 0F WILMINGTON, DELAWARE, ASSIGNOR TO THE JESS'UP&

MOORE PAPER C0., F PHILADELPHIA, PENNSYLVANIA, A CORPORATION 0F MASSA- CHUSETTS METHOD oF PRODUCING PUFFED PULP R Application led May 9, 1929. Serial No. 361,708.

This invention relates to the production of puEed pulp, particularly adapted for use in the manufacture of sheet `material on a paper making machine.

One of the objects of the invention is the production in an economical way of puifed pulp, which will exhibit a maximum per-` centage of curled fibers and contain a minimum amount of deleterious material.

Another object of the invention is to so l combine the soda process of producing pulp and recovering the valuable portions ofthe liquor drained and washed from the pulp, with my pulp puiiing method, as to el'ect a particularly economicalv operation.

The invention primarily involves subjectl ing the substantially dry pulp to impregnation by a strong caustic solution in a suitable impregnator, wherein the liquid content of i 'the mass will be limited in amount so thattheI diagrammatically a soda i pregnator which can be used in the puing operation, and means for supplying acaustic solution of regulated concentration to same.

Referring to Fig. 1, 5 designates a tank for receiving the caustic soda liquor of the desired' concentration, or stren h, for use in the cooking operation whic vis carried on in a digester, not shown.

The residue of colored liquondrained and.

washed from the cooked pulp 1s treated in a furnace designated 6 and the black ash vformed is then treated in )leachers designated 7 The resultant carbon is discharged from the system and the soda ash solution with the wash water and condensed steam is then discharged in a causticizing pan, designated 8, where it reacts with reburned lime to form a rst caustic alkali ofapproximately the highest strength which will permit thedesired reaction to proceed, sa for example, 16% sodium hydroxide (Na H) concentration. y

The clear solution is "decanted and discharged after dilution, as will be hereinafter described, into the tank 5. The residue, as shown in Fig. 1, passes to a second causticizing pan 8a, into which is discharged the decanted sodium hydroxide from pan .8b and caustic soda filtrate from lime iilter 9.'

The decanted sodium hydroxide in pan 8a, which wouldv be -somewhat less than half the strength of that discharged from pan ,8 (say, for example, approximately 7% concentration), is discharged into tank 5, and serves for diluting 'the sodium hydroxide discharged from tank 8, as previously described.

The residue from tank 8a is discharged into causticizing pan 8b, to which additional water is supplied. The sodium hydroxide decanted in this panV is discharged into pan 8a. l The residue from pan 8b is passed to a lime filter 9, which is supplied with a suitable quantity of water to recover the last traces of sodiumA hydroxide, which is passed tothe pan 8a.

The residue from the lime filter is passed A to a lime recovery plant and the reburned lime therefrom is supplied to the first caus-l vticizing pan 8.

As willrbe observed, the solution of sodium A hydroxide which is used for the cooking operation carried on in the digester consists of the liquor from the causticizing pan 8, of approximately 16% concentration, and the liquor from the caustic'izing pan'Sa, havingl approximately 7% concentration, so that the solution used in the digester has approximately a 10% concentration.

' .The volume of clear caustic solution discharged from pan 8a is in volume somewhat eater than thatdischarged from pan 8,

ile to the denser .settling of the carbonate y sludge in the weaker caustic solution.

rao

which reference is novv made.

n practicing this eXemplification of my invention, substantially dry fibrous cellulose pulp, or raw material is delivered to an Aimpregnating kneader l to Which is also delivered caustic alkali solution of sufficient strength, say 7% to 24%, to cause a curling of the fibres of the pulp upon impregnation. rThe caustic alkali is added only in such quantities that a resultant substantially nonfluid mass Will be produced, the mass containing at least 10% of fibrous material, the remainder of the mass being caustic soda or caustic alkali solution.

The impregnating kneader may consist of a Lannoye pulper or any suitable kneader, such as shown in Fig-4 in which the pressure producing means comprises thefweighted valve A and the caustic strength varying mean-s comprises separate valved conduits for Water and caustic leading to a mixing chamber B which feeds the kneader, in case it is desired to vary the strength of the caustic fed to the kneader.

The purpose of the impregnation is to cause the curling of the fibre of the cellulosic pulp mass and a swelling, or pulling, of such mass so that a highly absorbent sheet of felt material may subsequently be produced from the puffed pulp by a paper making machine.

Exposure to or contact with air is entirely unnecessary in the puffing, or curling of the fibres of the cellulose mass. The pulling takes place upon contact of the individual fibres With the strong caustic solution, regardless of the presence or absence of air in contact with the fibre. This pung is not demonstrated or apparent, however', until after thorough Washing out of all caustic and dissolved substances, such as slimy hemi-cellulose or cementacious substances. In fact, it is probably better not to expose the fibre and solution to the air before Washing. The caustic liquor may be said to have a mercerizing effect on the individual fibres which causes a swelling of the fibre casing and a skin tension unevenly distributed Which causes the fibre to curl.

The treatment of the cellulosic fibrous material with caustic soda results also in a dissolving `of the hemi-celluloses which are those carbohydrates which are insoluble in Water but soluble in dilute acids and alkalis. The dissolving of the hemi-celluloses causes a consequent increase in the highly resistant alpha-cellulose percentage of the finished product, thus accomplishing cellulose purification.

lt is desirable to entirely fill the pulper or kneader With the mass of pulp and caustic and to deliver the material thereto in such quantity that the mass of material and caustic alkali by reason of Weighted outlet valve A (Fig. 4), Will be under pressure Which will aid in the quicker impregnation of the fibrous mass With the sodium hydroxide solution.

AIt is also desirable to provide for varying the strength of the sodium hydroxide solution by mixing means B (F ig. 4) to compensate for variations in the moisture content of the substantially dry cellulosic material i being treated.

The pulp and caustic, after passing through the pulper Aor kneader, is then preferably passed to dehydrator la: Where the mass is Wrung or pressed to remove some of the strong treating caustic solution therefrom and to reuse the Arecovered strong solution in the impregnation in the kneader.

The mass of puffed or purified pulp and caustic as shown in Fig. 2 is then preferably passed into an agitator tank 2 Where more sodium hydroxide solution of weaker concentration is added causing the puffed pulp to become thoroughly impregnated and to be made fluid and of less consistency. The pulp and caustic is then transferred to a dehy* drator 3 where it is dehydrated and the caustic solution is Withdrawn, the pulp then being passed to a Washer 4f in which residual caustic is removed by Washing the purified or pued pulp With Water. The caustic solution Withdrawn from dehydrator 3 may be returned to the impregnating kneader and re used in the manner described with respect to dehydrator la.

The Washed puffed pulp is, then ready for formation into sheets of highly absorbent felt by means of a suitable paper making machine, not shown.

Fig. 3 is a flow sheet showing a method of 4combining the process of pufiing the pulp shown in Fig. 2, with the process of the preparation of the caustic alkali in the opera tion of a soda pulp mill as shown in Fig. l. According to the process of Fig. 3, the caustic alkali used in thepufing operation is reused in the regular pulp cooking operation Without any unusual dilution of the alkali solutions. Itis important to the accomplishment of this advantageous use and distribution of caustic alkali Without dilution, that substantially dry pulp be used at the start of the puffing operation. lThe pulp formed in the digesters is therefore substantially dehydrated' after Washing the black liquor therefrom, prior to starting the puifing operation.

Of course, other pulps may be used than that produced from caustic soda.

The combining of the pulling operation with the operation of the soda pulp mill' is accomplished according tothe present invention by pumping a portion of the strong (say about 16%), caustic liquor from causticizing pan 8 Which may or may not be fortified by stronger caustic, to the Lannoye pulper or impregnating kneader l, the other portion going to the digester strength solution tank 5 as before. The second liquor from pan 8a instead of passing directly to the digester solution receptacle 5 is passed directly to the agitator tank 2, and reaches the tank 5 indi= rectly after aiding in the puffing operation and passing through agitator tank 2 and dehydrator 3. The strong treating solution.

from the kneader also reaches the tank 5 after passing through dehydrator la, tank 2, and dehydrator 3.

A portion of the third liquor from pan 8b and the Weak dilute solution from the lime filter returns to pan 8a as before, While a portion thereof passes to agitator tank 2 with the second solution from pan 8a, through the dehydrator to tank 5. A further portion of the Weakest solutions (third liquor and lime filter solutions),v is pumped directly ,to the tank.

A very Weak caustic solution is obtained in the residual caustic Washer 4 and this 'solution is conveyed in part to lime filter 9 and in part to pan 8b.

It will thus be seen that the present invention provides a novel pulp puiing process combined With a soda pulp mill caustic recovery and pulp cooking process so as to conserve Without substantial dilution, the caustic liquors used in both the pulp cooking and puffing operations.

It Will be apparent that'mmodifications may be made Within the scope of the present invention and l do not desire to limitthe invention to the exact steps shown in the flow sheets, nor to the strengths of solution which are stated merely by Way of example.

The process of my invention is very rapid` in its treatment of the pulp to puff the fibres and may require as low as one-half to three quarters of a pound of alkali per pound of pulp material treated.

It will be understood that I do not confine my fibre treatment to fibres produced by any particular method but may use as a raW material fibres produced by the-soda, sulphate, or sulphite processes, either cooked or uncooked cotton ibres, reed, grass, or straw i cellulosic material, which may or may notA have been previously bleached.

The continuous feature of the methods as referred to inthe speciication and claims is intended to broadly refer to substantial 'continuity, as it Will be. apparent that the process can be carried out more or less intermittently.

While it is specified that a substantially non-fluid mass is produced Vin the pulp puff.- i ing operation, it is not desired t0 'restrict the invention to effecting dilution after the mass has been discharged from the pulper or kneader, since it will be apparent that the dilution of the non-fluid completely puffed mass could be readily effected in the pulper or kneader after the non-fluid mass is formed, Without departing from the scope of the invention.

It is also not desired to limit the invention to any particular ldiluting liquid.

I claim:

`1."The method of utilizing the caustic alkali solution of a soda pulp mill in' producing puffed pulp including the steps of supplying to. an impregnating kneader for the pulp a portion of the strong caustic solution from the iirst causticizing pan, the other portion passing to the supply of caustic alkali solution for cooking the Wood pulp, conveying the puffed pulp and caustic from the kneader to an agitating tank, conveying a second caustic liquor from a second causticizing pan to the agitator tank, conveying a portion of a third and fourth caustic liquor from a third caustici/zing pan and from a lime filter to said agitator tank, another portion of said third and fourth'liquors passing to the second causticizing pan, conveying the puffed purified and agitated pulp and caustic to a dehydrator and conveying the caustic solution from said dehydrator to said pulp cooking supply.

2. A method according to claim 1 including the step of passing a still further portion of said third and fourth liquors directly to said pulp cooking supply.

3. A method according to claim l including th steps of Washing the puffed pulp in a residual caustic Washer and conveying the Weak caustic thus obtained, in part to the third liquor and in part to the fourth liquor.

4. The continuous method of utilizing and economically conserving and reusing caustic alkali liquor for pulp cooking and for pulp puliing including the steps of delivering to a pulper a portion of the strongv caustic liquor from the first causticizing pan, delivering the other portion to the supply of Vcaustic for cooking the Wood pulp, conveying the puffed pulp and caustic from the pulper'to an agitat ing tank, conveying a second and weaker caustic liquor from a second causticizing pan to the agitator tank, conveying a portion of a third and fourth caustic liquor from a third caustic-izing pan and from a lime filter t0 said agitator tank, conveying another portion of said third and fourth caustic liquors to thev second causticizing pan, conveying a still further portion of said' third and fourth liquors4 directly to said pulp cooking supply,

livering the puffed pulp from said dehydra- .delivering the puffed and agitated pulp and tor to a residual caustic nwasher, Washing the puffed pulp and conveying the Weak caustic solution thus obtained, in part to the third liquor and in part to the fourth liquor.

5. The method of producing puffed pulp material comprising delivering substantially dry cellulosic fibrous pulp to an impregnating kneader, delivering caustic alkali to said impregnating kneader to produce in the kneader a puffing or curling of the fibres and to produce a substantially non-fluid mass, delivering said non-Huid mass to an agitator tank, delivering weaker caustic alkali to said agitator for further treatment of said mass, delivering said mass to a dehydrator, delivering the dehydrated mass to a residual caustic Washer, and delivering the Washed puffed fibrous pulp to a paper making machine and forming it into sheets of highly absorbent felt material.

6. The method of claim 5 in Which the-substantially dry cellulosic material is delivered to said kneader and maintained under pressure therein substantially out of contact with air, and in which the caustic alkali is supplied in such uniform quantity as to main tain the mass in the kneader over 10% consistency, and slightly varying the concentration of the uniform volume of the caustic alkali as to compensate for any variation in the moisture content ofthe substantially dry material supplied to the kneader.

7. The method of claim 5 in which the mass is partially dehydrated upon delivery from the impregnating-kneader and prior to delivery to the agitator tank, the portion of strong caustic solution thus recovered being returned to the impregnator for reuse.

8. The method of claim 5 including the step of returning the caustic solution delivered from said dehydrator to said impregnating kneader for reuse.

9. The method of vclaim 5 including the additional steps of partially dehydratng the mass upondelivery from the impregnating kneader and prior to delivery to the agitator, returning the portion of strong caustic thus recovered to the impregnator for reuse, and also returning to the impregnator the caustic solution delivered from the dehydrator which Jfollows the agitator.

10. The method of claim 5 in which the substantially dry cellulosic material is delivered to said kneader and maintained under pressure therein.

11.` The method of claim 4 including the step of dehydrating the puffed pulp and caustic mass prior to its delivery to the agitating tank and.l returning the thus recovered portion of strong treating caustic solution to the pulper for reuse.

12. The hereindescribed method of producing puffed pulp including treating substantially dry cellulosic fibrous pulp material in a kneader with caustic alkalisoluton of suiicient strength suchv as will produce a puffing ofthe pulp or curling of the fibres and in such volume of solution as to produce a resultant substantially non-fluid mass containing at least 10% of fibrous material, said resultant non-fluid mass as treated being of such density that there can be no free drainage, and Washing the material substantially free from caustic alkali and saponified substances. A,

13. The method of producing pued pulp material according to claim 12 including dehydrating the puffed fibrous non-iiuid mass and forming it into sheets of highly absorbent fibrous felt material.

.14. The method of cooking and puffing pulp comprising substantially continuously delivering caustic alkali liquor to digesters for cooking pulp and substantially continu ously delivering a portion of the same supply of caustic alkali to an impregnating kneader, treating substantially dry cellulosic fibrous pulp in said impregnating kneader with said caustic alkali to produce a substantially non-fluid mass of puffed libres, and delivering a substantial portion of the caustic alkali used in the puiiing operation to the digesters for cooking pulp. I

15. The method according to claim la including the steps of purifying the pufl'ed fibrous pulp, and delivering the purified puffed fibrous pulp to a paper making macliine'and forming it into sheets of highly absorbent felt material.

16. The method of cooking and puffing pulp comprising substantially continuously delivering caustic alkali liquor to digesters for cooking pulpvand substantially continu- `ously delivering a portion vof the same sup ply of caustic alkali to an impregnating j kneader', ytreating cellulosic fibrous pulp in said impregnating kneader With said caustic alkali to produce a mass of puffed fibres, and delivering a substantial portion of the caustic alkali used in the pulling operation to the digesters for cooking pulp.

17. The method of cooking and puing pulp comprising continuously or intermittently delivering caustic alkali liquor to digesters for cooking pulp and continuously or g intermittently delivering a portion of the same supply'of caustic alkali to an impregnating kneader in which is being treated a fibrous .cellulosic material in a substantially non-fluid condition to Which the caustic alkali has been added when said eellulosic material is in a substantially dry state, and returning a substantial ortion of the caustic alkali used in the puiimg operation for subsequent pulp cooking operations in the di- 1 gesters.

18. The method of producing puffed pulp material accordinor to lclaim l2 including diluting the puffed brous non-Huid mass, and t subsequently dehydrating the diluted mass. 1

19. A step in the method of producing puii'cd pulp consisting in impregnating the substantially dry pulp with a caustic alkali solution of approximately 16% concentration in an impregnator, and maintaining the liquid content of the mass in such limited amount that it will not exceed that required for producing a non-Huid mass.

20. A step in the method of producing l0 puffed pulp by curling the fibers thereof, this step consisting in impregnating the substantially dry pulp with a caustic-alkali solution, and maintaining the fluid content of the mass of pulp and solution in such limited amount that it will not exceed that required for producing a non-fluid mass.

In testimony whereof, I affix my signature.

JOSEPH E. PLUMSTEAD. 

